Determination of 129I in biomonitors collected in the vicinity of a nuclear power plant by neutron activation analysis

Neutron activation analysis (NAA) was used to determine ¹²⁹I and the ¹²⁹I/¹²⁷I ratio in bovine thyroid, moss, and river sediment samples collected in the vicinity of the Temelín nuclear power plant (NPP) in south Bohemia. The NAA procedures comprised pre-irradiation separation of ¹²⁹I by combustion of the samples in the stream of oxygen at 1,000 °C and trapping the liberated iodine in a LiOH/(NH₄)₂SO₃ solution. Post-irradiation separation of ¹³⁰I produced by the reaction ¹²⁹I(n,γ)¹³⁰I was carried out by extraction of elementary iodine with chloroform followed by precipitation of PdI₂. Nondestructive, epithermal NAA was used to determine ¹²⁷I employing the ¹²⁷I(n,γ)¹²⁸I reaction. The results showed that mean values of ¹²⁹I and the ¹²⁹I/¹²⁷I ratio in the bovine thyroids varied from 22 to 61 mBq kg^?1 (dry mass) and 2.8 × 10^?9 to 5.4 × 10^?9, respectively. These values are close to the lower end of results reported from various regions non-polluted with ¹²⁹I. No significant differences were found between ¹²⁹I concentrations and the ¹²⁹I/¹²⁷I ratios in the bovine thyroids collected prior to the start and after several years of operation of the NPP. The mean value and standard deviation of ¹²⁹I in mBq kg^?1, dry mass and the ¹²⁹I/¹²⁷I ratio in moss Pleurozium schreberi were 23 ± 16 and 2.3 × 10^?9, respectively, whereas values of ¹²⁹I in the river sediments were below 8–10 mBq kg^?1 (dry mass) after several years of the NPP operation.     

Study of chemoselective asymmetric hydrogenation of (1-bromo-1-alkenyl)boronic esters with iridium–PˆN complexes

In this paper we report the first chemoselective asymmetric hydrogenation of (1-bromo-1-alkenyl)boronic esters, which constitutes a new route to (α-bromoalkyl)boronic esters. The study demonstrates that excellent chemoselectivities along with full conversions can be obtained for hydrogenation of alkyl substituted derivatives with iridium–PˆN complexes. Moreover, acyclic alkyl derivatives afford (α-bromoalkyl)boronic esters in good enantioselectivities ranging from 64 to 73% ee. A cyclic alkyl derivative was obtained only in a nearly racemic form. The (1-bromo-1-alkenyl)boronic esters appear to be less reactive towards homogenous hydrogenation conditions than their chloro analogues as demonstrated by the higher catalyst loadings required to achieve full conversions for alkyl derivatives and lower conversions observed for the aryl substituted derivatives.     

Recognition of chiral anions using calix[4]arene-based ureido receptor in the 1,3-alternate conformation

A new type of calixarene-based receptor designed for the recognition of chiral anions was prepared by the introduction of (S)-2-methylbutan-1-ol moieties into the lower rim of calixarene. The immobilization of calixarene skeleton in the 1,3-alternate conformation enabled the construction of a cavity consisting of preorganised ureido functions and chiral substituents in close proximity. This cavity is capable of chiral discrimination of selected anions as demonstrated on d- and l-phenylalaninates.     

Highly sensitive determination of 68 psychoactive pharmaceuticals,illicit drugs,and related human metabolites in wastewater by liquid chromatography–tandem mass spectrometry

The present work describes the development and validation of a highly sensitive analytical method for the simultaneous determination of 68 compounds, including illicit drugs (opiates, opioids, cocaine compounds, amphetamines, and hallucinogens), psychiatric drugs (benzodiazepines, barbiturates, anesthetics, antiepileptics, antipsychotics, antidepressants, and sympathomimetics), and selected human metabolites in influent and effluent wastewater (IWW and EWW) by liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS). The method involves a pre-concentration and cleanup step, carried out by solid-phase extraction (SPE) using the adsorbent Strata-XC, followed by the instrumental analysis performed by LC–MS/MS, using a Kinetex pentafluorophenyl (PFP) reversed-phase fused-core column and electrospray ionization (ESI) in both positive and negative modes. A systematic optimization of mobile phases was performed to cope with the wide range of physicochemical properties of the analytes. The PFP column was also compared with two reversed-phase columns: fused-core C18 and XB-C18 (with a cross-butyl C18 ligand). SPE optimization and critical aspects associated with the trace level determination of the target compounds (e.g., matrix effects) have been also considered and discussed. Fragmentation patterns for all the classes were proposed. The validated method provides absolute recoveries between 75 and 120 % for most compounds in IWW and EWW. Low method limits of detection were achieved (between 0.04 and 10.0 ng/L for 87 % of the compounds), allowing a reliable and accurate quantification of the analytes at trace level. The method was successfully applied to the analysis of these compounds in five wastewater treatment plants in Santorini, a touristic island of the Aegean Sea, Greece. Thirty-two out of 68 compounds were detected in all IWW samples in the range between 0.6 ng/L (for nordiazepam) and 6,822 ng/L (for carbamazepine) and 22 out of 68 in all EWW samples, with values between 0.4 ng/L (for 9-OH risperidone) and 2,200 ng/L (for carbamazepine). The novel methodology described herein maximizes the information on the environmental analysis of these substances and also provides a first profile of 68 drugs in a Greek touristic area.     

聚焦形貌恢复方法模型设计

采用基于拉普拉斯算符聚焦形貌恢复方法,提出了模拟目标深度测量的数值模型。数值模拟的核心是基于通过几何光学预测的理想图像的卷积与透镜广义孔径函数的多色点扩散函数,即用聚焦误差替代抛物线圆柱形貌或高斯函数。该模型可以使用基于聚焦形貌恢复方法的传感器真实组件参数、光源光谱、光学系统离差、相机的光谱灵敏度。提出了光学系统离差（消球差、消色差、色差）对确定目标表面形貌的精确度和可靠性的影响。结果表明,该模型可以有效提高实验效率,缩短时滞,降低成本。     

Structural Elucidation of an Atropisomeric Entcassiflavan-(4β→8)-Epicatechin Isolated from Dalbergia monetaria L.f. Based on NMR and ECD Calculations in Comparison to Experimental Data

A rare dihydoxyflavan-epicatechin proanthocyanidin, entcassiflavan-(4β→8)-epicatechin, was isolated from Dalbergia monetaria, a plant widely used by traditional people from the Amazon to treat urinary tract infections. The constitution and relative configuration of the compound were elucidated by HR-MS and detailed 1D- and 2D-NMR measurements. By comparing the experimental electronic circular dichroism (ECD) spectrum with the calculated ECD spectra of all 16 possible isomers, the absolute configuration, the interflavan linkage, and the atropisomers could be determined.     

Microporosity of a Guanidinium Organodisulfonate Hydrogen‐Bonded Framework

Guanidinium organosulfonates (GSs) are a large and well‐explored archetypal family of hydrogen‐bonded organic host frameworks that have, over the past 25 years, been regarded as nonporous. Reported here is the only example to date of a conventionally microporous GS host phase, namely guanidinium 1,4‐benzenedisulfonate ( p ‐G₂BDS ). p ‐G₂BDS is obtained from its acetone solvate, AcMe@ G₂BDS , by single‐crystal‐to‐single‐crystal (SC‐SC) desolvation, and exhibits a Type I low‐temperature/pressure N₂ sorption isotherm (SA_BET=408.7(2) m² g^?1, 77 K). SC‐SC sorption of N₂, CO₂, Xe, and AcMe by p ‐G₂BDS is explored under various conditions and X‐ray diffraction provides a measurement of the high‐pressure, room temperature Xe and CO₂ sorption isotherms. Though p ‐G₂BDS is formally metastable relative to the “collapsed”, nonporous polymorph, np ‐G₂BDS , a sample of p ‐G₂BDS survived for almost two decades under ambient conditions. np ‐G₂BDS reverts to zCO₂@ p ‐G₂BDS or yXe@ p ‐G₂BDS (y,z=variable) when pressure of CO₂ or Xe, respectively, is applied.     

Versatile post-functionalisation strategy for the formation of modular organic–inorganic polyoxometalate hybrids

Hybrid structures incorporating different organic and inorganic constituents are emerging as a very promising class of materials since they synergistically combine the complementary and diverse properties of the individual components. Hybrid materials based on polyoxometalate clusters (POMs) are particularly interesting due to their versatile catalytic, redox, electronic, and magnetic properties, yet the controlled incorporation of different clusters into a hybrid structure is challenging and has been scarcely reported. Herein we propose a novel and general strategy for combining multiple types of metal-oxo clusters in a single hybrid molecule. Two novel hybrid POM structures (HPOMs) bis-functionalised with dipentaerythritol (R–POM₁–R; R = (OCH₂)₃CCH₂OCH₂C(CH₂OH)) were synthesised as building-blocks for the formation of heterometallic hybrid triads (POM₂–R–POM₁–R–POM₂). Such a modular approach resulted in the formation of four novel heterometallic hybrids combing the Lindqvist {V₆}, Anderson–Evans {XMo₆} (X = Cr or Al) and trisubstituted Wells–Dawson {P₂V₃W₁₅} POM structures. Their formation was confirmed by multinuclear Nuclear Magnetic Resonance (NMR), infrared (IR) and UV-Vis spectroscopy, as well as Mass Spectrometry, Diffusion Ordered Spectroscopy (DOSY) and elemental analysis. The thermal stability of the hybrids was also examined by Thermogravimetric Analysis (TGA), which showed that the HPOM triads exhibit higher thermal stability than comparable hybrid structures containing only one type of POM. The one-pot synthesis of these novel compounds was achieved in high yields in aqueous and organic media under simple reflux conditions, without the need of any additives, and could be translated to create other hybrid materials based on a variety of metal-oxo cluster building-blocks.

A versatile modular approach has been developed for incorporating different metal-oxo nanoclusters with characteristic structures into a single hybrid molecule by covalently linking them with polyol ligands.